The miniaturization and packaging of electrical and electronic circuit components, particularly those intended for millimeter and microwave applications, such as GaAs monolithic integrated circuit devices, has led to the need for an associated interconnect structure, which not only acts as a support fixture for the various building blocks of an overall signal processing system, but contains the requisite (transmission line) interconnect between components. One particularly useful structure that has been developed for this purpose is described in U.S. Pat. No. 4,695,810 to D. Heckaman et al, issued Sept. 22, 1987 and assigned to the Assignee of the present application. This patented transmission line/support fixture, termed `waffleline`, is similar in appearance to the structure of a waffle iron, in that it is comprised of a conductive plate whose surface is configured as an array of mesas separated from one another by a gridwork of troughs or channels. The `waffleline` plate may also contain pockets, recessed areas or apertures in which MMIC components are supported, connections among which are effected by installing insulated wires along the channels. In its installed condition, a length of insulation-clad wire serves as the center conductor of a periodic transmission line, the characteristic impedance of which (e.g. 50 ohms) is established by the dimensional spacing and sizes of the channels and mesas of the plate, which also forms the ground plane of the transmission line. Because the operational frequency of the components supported by a `waffleline` plate is in the multi (tens of) GHz range, both the size of the center conductor (e.g. 0.021 inch diameter wire) and the channel spacing between mesas (0.025 inches channel width and depth, corresponding to a period of 50 mils) are extremely small, placing a significant precision requirement on the process through which the center conductor is installed in the channels of the waffleline.